It is the primary objective of this project to measure the level of cyclic nucleotide metabolism in human retina obtained at autopsy. Samples of retina will be examined for gross and histological pathology and assayed biochemically for the activities of adenyl cyclase and guanyl cyclase and the kinetic classes of cyclic AMP and cyclic GMP phosphodiesterase. From these data we can evaluate the activity of the enzymes of cyclic nucleotide metabolism in normal retina and determine whether abnormalities in these enzymes activities might be related to conditions of retinal degeneration.